OTTAWA — Two key losses led to the Lightning’s second consecutive loss.

Tampa Bay played most of Thursday without starting goaltender Ben Bishop and top line center Valtteri Filppula before falling 5-3 to Ottawa in front of an announced crowd of 19,757 at Canadian Tire Centre.

Bishop went down to injury in the opening two minutes of the game while Filppula was lost in the early stages of the second period.

The Senators took advantage of the absences and pulled away before Tampa Bay closed the gap with a pair of late third-period goals - a shorthanded goal by Tyler Johnson as well as a goal from Victor Hedman.

Lightning captain Marty St. Louis registered his 600th career assist on the final goal, while his 965th career point pulled him into a tie for 85th on the all-time scoring list with Rocket Richard.

The back-to-back regulation losses mark the first time the Lightning have dropped consecutive regulation games since Nov. 29 and Dec. 3 when they were shutout in back-to-back games by Pittsburgh and Columbus. Tampa Bay’s lead over Toronto for second place in the Atlantic Division was cut to three points.

Both Bishop and Filppula said after the game they were feeling better, leaving more concern for how the game transpired.

“We lose a couple of pretty important players on our team, but that’s not why we lost the game. We just got outplayed,’’ Lightning head coach Jon Cooper said.

It didn’t help that Ottawa scored the first goal of the game when Marc Methot scored into an empty net 1:49 into the first period as Bishop lay prone on the ice inside the right circle. As Bishop came out to poke a loose puck away from a charging Mike Zibanejad, the goaltender dove forward onto his stomach, which forced teammate Nikita Kucherov to try to jump over him. But Kucherov appeared to make contact with his left skate boot to the back of Bishop’s head, leaving Bishop down on the ice for several minutes before getting up and skating to the locker room under his own power.

After being initially stunned, Bishop said he felt better by the end of the game and said he passed the concussion protocol, while complaining of a minor headache that had begun to diminish.

“It didn’t feel very good, a little bit of a headache, but it’s gotten better as the game went on,’’ said Bishop, who reported he has never been diagnosed with a concussion. “No dizziness, but I felt a little weak after I got hit. Hopefully I’ll wake up (Friday) and feel good and be able to practice.’’

Kucherov said he tried to leap over Bishop as best he could.

“I saw him almost in the last second, I didn’t know what to do, I tried to go on my right leg and lift my left leg,’’ Kucherov said. “I didn’t know I hit him because I didn’t feel it. Then they score a goal and I looked around and see him lying there.’’

Anders Lindback came on in relief and held the fort as Ottawa surged before the Senators made it 2-0 when Erik Karlsson scored with 24.7 seconds left in the period. Alex Killorn made it 2-1 at 3:10 of the second, but Ottawa would pull away with three consecutive goals after Filppula was injured after a collision in the offensive zone on the opening shift of the second period. Filppula returned briefly, but took only one shift at the 6:25 mark of the second period and did not return with an unspecified lower-body injury.

“I didn’t feel good and I was concerned it might get worse, so I felt the smartest thing was to come off,’’ Filppula said. “We’ll see, the next few days will tell more about how I’m feeling, but I hope I can come back right away. It’s too early to say right now, we’ll know more in the morning on how I feel.’’

Tampa Bay mounted a bit of a late comeback, firing 23 shots on goal - a single period season high - and scoring twice but were unable to overcome poor play from earlier in the game.

“We were desperate the last few minutes, but we need that desperation from the start,’’ St. Louis said.